JP2008082209A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a suction structure for an internal combustion engine miniaturizing a cylinder head by reducing extrusion to an outside of a suction port in an internal combustion engine whose suction valve reciprocates in parallel with a reciprocating direction of the piston. <P>SOLUTION: The internal combustion engine has the suction valve supported reciprocatably in parallel with a reciprocating direction of the piston 44 by a cylinder head 33 having a suction port 43 formed integrally, and provided with a fuel injection device 21I integrated with a throttle body 21 on a suction manifold 20 connected to the suction port 43. The suction port 43 extending to a cylinder head cover 34 side along a recessed part 33a formed on an outside surface of the cylinder head 33 is connected to a suction manifold 20 before the same gets to a same level as a mating surface 180u of the cylinder head 33 and the cylinder head cover 34. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an intake structure for an internal combustion engine.

  An internal combustion engine having a structure in which an intake valve reciprocates in parallel with a reciprocating direction of a piston and a cam of a cam shaft directly presses the intake valve is known (see, for example, Patent Document 1).

Japanese Patent Publication No. 1-16983

  In such an internal combustion engine, since the reciprocating direction of the piston and the reciprocating motion of the intake valve are parallel, the opening surface of the intake port that opens to the combustion chamber is parallel to the mating surface of the cylinder head with the cylinder block. The intake port bends from the open surface and extends obliquely upward, and further extends to the outside from the side wall of the cylinder head.

The intake port disclosed in Patent Document 1 protrudes outward from the side wall of the cylinder head and extends upward to reach the mating surface of the cylinder head with the cylinder head cover, and is connected to an intake pipe (intake manifold) from there. The pipe extends in a curved manner so as to straddle the cylinder head cover.
A fuel injection nozzle is provided in the intake pipe.

  The intake port that protrudes outward from the cylinder head bulges outward and extends upward to the mating surface of the cylinder head with the cylinder head cover, so the intake port protrudes outward from the cylinder head and the cylinder head is large. It has become.

  The present invention has been made in view of the above points, and an object of the present invention is to reduce the outward protrusion of the intake port in an internal combustion engine in which the intake valve reciprocates in parallel with the reciprocating direction of the piston. This is to provide an intake structure for an internal combustion engine in which the cylinder head is miniaturized.

  In order to achieve the above object, according to the first aspect of the present invention, an intake valve is supported reciprocally in parallel with a reciprocating direction of a piston on a cylinder head integrally formed with an intake port, and connected to the intake port. In the internal combustion engine in which the fuel injection device integrated with the throttle body is provided in the intake manifold, the intake port extending toward the cylinder head cover along the recess formed in the outer surface of the cylinder head is The intake structure of the internal combustion engine is connected to the intake manifold before reaching the same surface as the mating surface with the cylinder head cover.

  According to a second aspect of the present invention, there is provided an intake structure for an internal combustion engine according to the first aspect, wherein the intake port and the intake air are provided on a side of a lifter guide hole of the cylinder head that slidably supports a valve lifter of the intake valve. The connecting portion with the manifold is located.

  According to a third aspect of the present invention, in the intake structure of the internal combustion engine according to the first or second aspect, a camshaft that directly presses the intake valve is located on a mating surface of a cylinder head and a cylinder head cover, and the cylinder head The cylinder head cover that is overlapped with the cylinder head also has a recess continuous with the recess of the cylinder head, and the intake manifold connected to the intake port extends along the recess of the cylinder head cover. To do.

  According to the intake structure for an internal combustion engine according to claim 1, the intake port extending toward the cylinder head cover along the recess formed in the outer surface of the cylinder head is flush with the mating surface of the cylinder head and the cylinder head cover. The cylinder head can be reduced in size because it is connected to the intake manifold immediately before reaching.

  According to the intake structure of the internal combustion engine according to claim 2, the connecting portion between the intake port and the intake manifold is located on the side of the lifter guide hole of the cylinder head that slidably supports the valve lifter of the intake valve of the cylinder head. Therefore, the lifter guide hole can be protected by the intake manifold.

  According to the intake structure of the internal combustion engine according to claim 3, since the intake manifold connected to the intake port extends along the recess of the cylinder head cover continuous with the recess of the cylinder head, the cylinder head and the cylinder head cover are aligned. The intake manifold can protect the camshaft located on the surface.

Hereinafter, an embodiment according to the present invention will be described with reference to FIGS.
FIG. 1 is a side view showing a state where a vehicle body cover and the like of a rough terrain vehicle 1 mounted with a water-cooled internal combustion engine E according to the present embodiment is mounted, and FIG.
In the present embodiment, the front, rear, left and right are determined based on the state in which the vehicle is directed forward.

  The rough terrain vehicle 1 is a saddle-ride type four-wheel vehicle, and includes a pair of left and right front wheels FW to which low pressure balloon tires for rough terrain are mounted, and a pair of left and right rear wheels RW to which the same balloon tires are mounted. It is suspended before and after the body frame 2.

  The body frame 2 is formed by combining a plurality of types of steel materials, and includes a center frame portion 3 on which a power unit P in which an internal combustion engine E and a transmission T are integrally formed in a crankcase 31 is mounted, and the front of the center frame portion 3. The front frame portion 4 is connected to the front portion and the rear frame portion 5 has a seat rail 6 that supports the seat 7 and is connected to the rear portion of the center frame portion 3.

  The center frame portion 3 has a pair of left and right upper pipes 3a bent in the front and rear directions to form approximately three sides, and another pair of left and right lower pipes 3b connected to each other to form a generally rectangular shape in side view. The pipe is configured by connecting cross members.

  A swing arm 9 pivotally supported at the front end is swingably provided on a pivot plate 8 fixed to a portion of the lower pipe 3b that is bent and extended obliquely upward, and the rear portion of the swing arm 9 and the rear frame portion 5 are swingably provided. A rear cushion 10 is interposed therebetween, and a rear wheel RW is suspended from a rear final reduction gear unit 19 provided at the rear end of the swing arm 9.

  A steering column 11 is supported at the center in the width direction of the cross member installed between the front end portions of the left and right upper pipes 3a, and a steering handle 13 is attached to an upper end portion of a steering shaft 12 supported by the steering column 11 so as to be steerable. And the lower end of the steering shaft 12 is connected to the front wheel steering mechanism 14.

The internal combustion engine E of the power unit P is a water-cooled two-cylinder internal combustion engine, and is mounted on the center frame portion 3 in a so-called vertical posture with the crankshaft 30 oriented in the longitudinal direction of the vehicle body.
The transmission T of the power unit P is disposed on the left side of the internal combustion engine E, and an output shaft 80 directed in the front-rear direction projects from the transmission T near the left side. The rotational power of the output shaft 80 is It is transmitted from the front end of the output shaft 80 to the left and right front wheels FW via the front drive shaft 16 and the front final reduction gear unit 17, and from the rear end to the left and right rear wheels via the rear drive shaft 18 and the rear final reduction gear unit 19. Is transmitted to the RW.

  A radiator 27 is supported on the front frame portion 4 of the vehicle body frame 2, and an oil cooler 28 is disposed in front of the radiator 27.

  Referring to FIG. 3 which is a rear view of the power unit P, a crankcase 31 that internally constitutes the internal combustion engine E and the transmission T of the power unit P is an upper crankcase 31U that is divided vertically by a plane including the crankshaft 30. And a lower crankcase 31L.

A cylinder block part 32 formed integrally with two cylinder bores 32c arranged in series is formed on the upper part of the upper crankcase 31U so as to be inclined to the left and extend upward. The cylinder head 33 is overlapped, and the cylinder head cover 34 is put on the cylinder head 33.
On the other hand, an oil pan 35 is attached under the lower crankcase 31L.

  An intake manifold 20 that curves from the right side wall of the cylinder head 33 and extends substantially upward is provided with a fuel injection device 21I along with the throttle body 21, and an intake connection pipe 29 connected to the throttle body 21 is an internal combustion engine. An exhaust pipe 23 connected to an air cleaner 22 disposed above E and curved leftward from the left side wall of the cylinder head 33 is connected to an exhaust muffler 24 attached to the left side of the rear frame portion 5. .

Fuel is supplied to the fuel injection device 21I from a fuel tank 26 disposed behind the power unit P.
In addition, since the fuel injection device 21I is integrated with the throttle body 21, there is no need to separately form a member that supports the fuel injection device 21I, so that the cost of the fuel injection device 21I can be reduced.

  3 and 4, the piston 40 is fitted to the two cylinder bores 32c of the cylinder block 32 so as to be slidable back and forth, and the crank pin 30p between the crank webs 30w and 30w of the crankshaft 30 and the piston 40 A connecting rod 41 is connected to the piston pin 40p to constitute a crank mechanism.

The cylinder head 33 has, for each cylinder bore 32c, a combustion chamber 42 formed facing the piston 40, and an intake port 43 that opens to the combustion chamber 42 and is opened and closed by a pair of intake valves 45 on the right and above. An exhaust port 44 that opens and closes by a pair of exhaust valves 46 extends forward, and a spark plug 47 that faces the combustion chamber 42 is mounted.
The intake manifold 20 is connected to the intake port 43.
By adjusting the length of the intake manifold 20, the throttle body 21 can be separated from the cylinder head 33 by a predetermined distance, and the throttle body 21 can be protected from heat.

  In this cylinder head 33, an intake valve 45 is supported so as to be able to reciprocate in parallel with the reciprocating direction of the piston 40. Therefore, the valve stem 45s of the intake valve 45 is parallel to the central axis of the cylinder bore 32c, and the combustion chamber 42 The opening surface of the intake port 43 that opens to the cylinder head 33 is parallel to the mating surface of the cylinder head 33 with the cylinder block 32.

The upper end of the intake valve 45 abuts on the intake cam lobe 48i of the cam shaft 48 rotatably supported by the cylinder head 33, and one end of the rocker arm 50 pivotally supported by the rocker arm shaft 49 contacts the exhaust cam lobe 48e of the cam shaft 48. The upper end of the exhaust valve 46 is in contact with the other end of the rocker arm 50.
Therefore, in synchronization with the rotation of the crankshaft 30 by the camshaft 48, the intake valve 45 and the exhaust valve 46 open and close the intake port 43 and the exhaust port 44, respectively, at a predetermined timing.

  For this purpose, the camshaft 48 is fitted with a cam sprocket 48s at the rear, and a timing chain 51 is spanned between the drive sprocket 30s and the cam sprocket 48s fitted near the rear end of the crankshaft 30 (see FIG. 4) and is driven to rotate at half the rotational speed of the crankshaft 30.

  The crankshaft 30 is sandwiched between the upper crankcase 31U and the lower crankcase 31L via a plain bearing 52 and is rotatably supported. As shown in FIG. 4, the crankshaft 30 protrudes rearward from the crank chamber of the crankshaft 30. The drive sprocket 30s is formed on the side portion, and a primary drive gear 56 is provided on the rear end portion thereof via a fluid coupling 55 that is a fluid coupling.

The fluid coupling 55 includes a pump impeller 55p fixed to the crankshaft 30, a turbine runner 55t facing the pump impeller 55p, and a stator 55s.
The primary drive gear 56a is coupled to a turbine runner 55t that can rotate with respect to the crankshaft 30, and the power from the crankshaft 30 is transmitted to the primary drive gear 56a via hydraulic oil.
The primary drive gear 56a meshes with a primary driven gear 56b that is supported by the main shaft 61, which will be described later, and transmits the rotation of the crankshaft 30 to the main shaft 61 side.

On the other hand, a starting driven gear 59 is pivotally supported on the front side portion of the crankshaft 30 protruding forward from the crank chamber C via an AC generator 57 and a one-way clutch 58.
A balancer shaft driving gear 54 is fitted to a portion of the crankshaft 30 along the inner surface of the front wall of the crank chamber C.

A transmission chamber M is formed by a partition wall on the left side of the crank chamber C that houses the crank web 30w of the crankshaft 30.
The transmission gear mechanism 60 housed in the transmission chamber M is a constantly meshing gear mechanism, and a main shaft 61 is pivotally supported on the upper crankcase 31U at an obliquely upper position on the left side of the crankshaft 10, and the main shaft A counter shaft 71 is pivotally supported by being sandwiched between the split surfaces of the upper and lower crankcases 31U and 31L at a position diagonally downward to the left of 61 and to the left of the crankshaft 30 (see FIG. 3).

  The main shaft 61 includes an inner cylinder 61i and an outer cylinder 61o that is rotatably fitted to a part of the inner cylinder 61i. The front end of the inner cylinder 61i is formed on the front side wall 31f of the transmission chamber M of the upper crankcase 31U. The bearing recess 62 is rotatably supported via a bearing 62b, and an outer cylinder 61o is fitted in a substantially central position on the rear side of the inner cylinder 61i so as to be relatively rotatable. The portion is rotatably supported by a bearing opening 63 formed in the rear side wall 31r of the transmission chamber M via a bearing 63b, and is supported together with the inner cylinder 61i.

In the outer cylinder 61o, the second speed change drive gear m2 and the fourth speed change drive gear m4 are integrally formed on the inner side of the bearing 63b in the front and rear, and a part of the outer side of the outer cylinder 61o protrudes outward from the bearing 63b.
The inner cylinder 61i is integrally formed with the first transmission driving idle gear m1 and the shifter in order from the front in front of the second and fourth transmission driving gears m2 and m4 of the outer cylinder 61o and is spline-fitted to the inner cylinder 61i. A fifth transmission drive gear m5 and a third transmission drive idle gear m3 are pivotally supported, and an outer portion of the inner cylinder 61i protrudes further rearward than the outer portion of the outer cylinder 61o.

  The bearing recess 62 formed in the front side wall 31f has a small inner diameter so as to support the front end of the small-diameter inner cylinder 61i, whereas the bearing opening 63 formed in the rear side wall 31r has a maximum diameter. It has an inner diameter smaller than that of the fifth transmission drive gear m5 but larger than the diameter of the fourth transmission drive gear m4, and is used for assembling the main shaft 61.

An input sleeve 65 is rotatably fitted to the outer part of the inner cylinder 61i along with the outer cylinder 61o, and the primary driven gear 56b is fitted in the center of the input sleeve 65, and the primary driven gear 56b is cranked. It meshes with the primary drive gear 56a on the shaft 30 side.
A first transmission clutch 66 is assembled to the rear of the input sleeve 65 from the primary driven gear 56b, and a second transmission clutch 67 is assembled to the front of the primary driven gear 56b.

The pair of first transmission clutch 66 and second transmission clutch 67 are hydraulic multi-plate friction clutches having the same structure.
In the first transmission clutch 66, a hook-like clutch outer 66o opened rearward is integrally fitted to the input sleeve 65, and a clutch inner 66i is integrally fitted to the inner cylinder 61i.
On the other hand, in the second transmission clutch 67, a hook-like clutch outer 67o that opens forward is integrally fitted to the input sleeve 65, and a clutch inner 67i is integrally fitted to the outer portion of the outer cylinder 61o.

  When hydraulic pressure is supplied to the first transmission clutch 66 and the clutch outer 66o and the clutch inner 66i are connected, the rotation of the input sleeve 65 integral with the primary driven gear 56b is rotated by the second and fourth speed change drive gears m2, When the hydraulic pressure is not supplied to the rotation of m4, the clutch outer 66o and the clutch inner 66i are disconnected, and the rotation is not transmitted to the second and fourth speed change drive gears m2 and m4 of the outer cylinder 61o.

  Similarly, when hydraulic pressure is supplied to the second transmission clutch 67 and the clutch outer 67o and the clutch inner 67i are connected, the rotation of the input sleeve 65 integral with the primary driven gear 56b is transmitted to the inner cylinder 61i and is transmitted to the inner cylinder 61i. When the fifth transmission drive gear m5 fitted with the spline is rotated and no hydraulic pressure is supplied, the clutch outer 67o and the clutch inner 67i are disconnected, and the rotation is not transmitted to the fifth transmission drive gear m5 on the inner cylinder 61i.

  The counter shaft 71 pivotally supported between the upper and lower crankcases 31U and 31L at a diagonally lower position on the left side of the main shaft 61 as described above has a front side portion on the front side wall 31f of the mission chamber M. The formed bearing opening 72 is rotatably supported via a bearing 72b, and the rear end is rotatably supported by a bearing recess 73 formed in the rear side wall 31f of the mission chamber M via a bearing 73b. Be supported.

A third shift driven gear n3 integrally formed with the first shift driven gear n1, the fifth shift driven idle gear n5, and the shifter in order from the front side in the transmission chamber M in the mission chamber M is spline-fitted to the counter shaft 71. The reverse idle gear nR, the second shift driven idle gear n2, the shifter nS, and the fourth shift driven idle gear n4 are pivotally arranged.
The corresponding shift drive gear and shift driven gear are always meshed.

  A reverse idle shaft 70 is disposed above the counter shaft 71 (see FIGS. 3 and 4), and a reverse large-diameter gear r1 and a reverse small-diameter gear r2 are integrally rotatable on the reverse idle shaft 70. The reverse large-diameter gear r1 is engaged with the second speed change drive gear m2 on the main shaft 61, and the reverse small-diameter gear r2 is engaged with the reverse idle gear nR on the counter shaft 71.

The fifth shift drive gear m5 on the main shaft 61 and the third shift driven gear n3 on the counter shaft 71 are shifter gears. The two shifter gears and the shifter nS on the counter shaft 71 are axially moved by the shift drive mechanism. The gear position is configured by being moved.
That is, the fifth speed drive gear m5 moves forward and backward to form the first speed and the third speed, the third speed driven gear n3 moves forward and backward to form the fifth speed and reverse, and the shifter nS moves back and forth to the second speed. A stage and a fourth speed stage are configured.
This gear shift control and the control of the first shift clutch 66 and the second shift clutch 67 are combined to transmit power to each shift step.

The front end of the counter shaft 71 protrudes forward from the bearing 72b, and an output gear 74 is spline-fitted to the front end.
The output shaft 80 is disposed obliquely right below the counter shaft 71 (see FIG. 3), and a driven gear 75 that is spline-fitted to the front portion of the output shaft 80 is connected to the front end of the counter shaft 71. The power is transmitted from the counter shaft 71 to the output shaft 80 by meshing with the output gear 74.

Since a large load is applied to the output gear 74 at the front end of the counter shaft 71 by meshing with the driven gear 75 of the output shaft 80, a bearing 72b that supports the front portion of the counter shaft 71 is configured using a relatively large one. ing.
Therefore, the inner diameter of the bearing opening 72 that fits the bearing 72b in the front side wall 31f is increased, but the bearing recess 62 of the adjacent main shaft 61 is formed with a small diameter as described above. The strength of the front side wall 31f of the crankcase 31 can be maintained high.

  A front case cover 85 is placed on the front surface of the upper and lower crankcases 31U and 31L, which are divided into upper and lower parts, on which the counter shaft 71 and the output shaft 80 protrude, and the rear surfaces of the upper and lower crankcases 31U and 31L are covered. The rear case cover 150 also serves as a case cover so as to cover the fluid coupling 55 at the rear end of the crankshaft 30 and the first and second transmission clutches 66 and 67 at the rear end of the main shaft 61 across the split surface. It is covered via a spacer 110.

The output shaft 80 is configured by connecting a forged-formed front end bearing portion 81 and a rear end bearing portion 82 to a hollow cylindrical member 83, and the front end bearing portion 81 is formed on the front case cover 85. The bearing 86b is inserted into the bearing opening 86 so that the front end protrudes forward, and the rear end supported portion 82 is supported by the bearing opening 111 formed in the spacer 110. It is pivotally supported by protruding backward.
That is, the output shaft 80 is rotatably supported by the front case cover 85 and the spacer 110, respectively, with the front end bearing portion 81 and the rear end bearing portion 82 protruding front and rear.

The driven gear 75 is spline fitted to the front end bearing portion 81 adjacent to the inside of the bearing 85b.
Accordingly, the output gear 74 at the front end of the counter shaft 71 is engaged with the driven gear 75 that is spline-fitted to the front end bearing portion 81 of the output shaft 80, and power is transmitted from the counter shaft 71 to the output shaft 80.

  Since the output shaft 80 is configured by connecting the forged-formed front end bearing portion 81 and the rear end bearing portion 82 to the hollow cylindrical member 83, the output shaft 80 can be reduced in weight and conventionally Thus, the forging device can be reduced in size compared to forging the entire output shaft.

On the other hand, a balancer shaft 90 is pivotally supported between the split surfaces of the upper and lower crankcases 31U and 31L at the right side of the crankshaft 30 (see FIG. 3).
Referring to FIG. 5, the balancer shaft 90 includes bearings 91b and 92b in bearing openings 91 and 92 formed at the front and rear side walls of the upper and lower crankcases 31U and 31L, respectively. Thus, it is pivotally supported.

  The balancer shaft 90 is arranged as close to the crankshaft 30 as possible. As shown in FIG. 5, the balancer weight 90w of the balancer shaft 90 is connected to the crank web 30w of the crankshaft 30 in the crankshaft direction (front-rear direction). (The counter weight) and the positional relationship.

A driven gear 93 is spline-fitted adjacent to a bearing 91b fitted to the front end of the balancer shaft 90 on the inside, and the driven gear 93 is connected to the balancer shaft driving gear 54 fitted to the crankshaft 30. The rotation of the crankshaft 30 is transmitted to the balancer shaft 90 at the same rotational speed.
Therefore, the primary vibration caused by the reciprocating motion of the piston 40 is canceled by the rotation of the balancer shaft 90 at the same speed as the crankshaft 30.

  A water pump 95 provided on a front cover member 87 that covers the AC generator 57 and the like from the front is disposed in front of the balancer shaft 90, and is freely rotatable on a bearing tube portion 87a of the front cover member 87. A pivotally supported water pump drive shaft 96 is arranged coaxially with the balancer shaft 90.

Then, a connecting convex portion 90f protruding forward from the front end of the balancer shaft 90 and a connecting concave portion 96a formed at the rear end of the water pump drive shaft 96 are fitted, and the rotation of the balancer shaft 90 is transmitted to the water pump drive shaft 96. Then, the water pump 95 is driven.
A water pump cover 97 having a suction cylinder 97a is put on the front side of the water pump 95.
The suction cylinder 97a of the water pump cover 97 is connected to the radiator 27 disposed in front of the vehicle body by a water pipe, and the water pump 95 sucks cooling water from the radiator 27.

  On the other hand, an oil pump unit 100 provided in the spacer 110 is disposed behind the balancer shaft 90, and an oil pump drive shaft 101 rotatably supported by the oil pump unit 100 is connected to the balancer shaft. It is arranged coaxially with 90.

  Then, a connecting recess 90r formed at the rear end of the balancer shaft 90 and a connecting projection 101a protruding at the front end of the oil pump drive shaft 101 are fitted, and the rotation of the balancer shaft 90 is transmitted to the oil pump drive shaft 101 to be The pump unit 100 is driven.

  The lubrication of the power unit P employs a dry sump method, and the oil pump drive shaft 101 in the oil pump unit 100 has a structure in which each of the scavenge pump 102 and the feed pump 103 rotor is attached.

  As described above, since the water pump drive shaft 96 is coaxially connected to the front end of the balancer shaft 90 and the oil pump drive shaft 101 is coaxially connected to the rear end, the three axes are configured coaxially and separated from each other parallel to the crankshaft 30. Since the number of rotating shafts can be reduced and a complicated power transmission mechanism is not required between the rotating shafts, the internal combustion engine can be reduced in size.

  In addition, since the balancer shaft 90 is disposed at a position where the crank web 30w and the balancer weight 90w of the crankshaft 30 overlap in the axial direction, the balancer shaft 90 approaches the crankshaft 30 and further increases the amount of the internal combustion engine E. Miniaturization is achieved.

The structure of the cylinder head 33 of the internal combustion engine E as described above is shown in FIGS.
FIG. 7 is a plan view of the cylinder head 33.
As shown in FIG. 7, the cylinder head 33 has an outer wall 180 that forms a substantially rectangular frame in the front and rear, and the upper end surface of the outer wall 180 is a mating surface 180 u with the cylinder head cover 34. .

  Two openings of the intake port 43 and two openings of the exhaust port 44 are formed in each combustion chamber 42 corresponding to both cylinder bores 32c, 32c, and a cylindrical valve guide cylinder 181i is formed corresponding to the opening of the intake port 43. A circular lifter guide hole 182i is formed, and a cylindrical valve guide cylinder 181e is fitted into the exhaust port 44 corresponding to the opening of the exhaust port 44 to form a circular guide hole 182e.

The two intake ports 43 extending obliquely upward to the right from the two openings of the combustion chamber 42 merge into one and are slightly curved and extend substantially upward.
The two exhaust ports 44 extending diagonally to the left from the two openings of the combustion chamber 42 merge into one and are slightly curved and extend to the left.

Between the lifter guide holes 182i, 182i on the intake port 43 side, a bearing portion 183 having a semicircular arc portion that rotatably supports the cam shaft 48 is formed.
The bearing portion 183 is formed with a semicircular arc portion 183a that supports the cam shaft 48 on the upper end surface that is flush with the mating surface 180u.
The cam shaft 48 is rotatably supported via a bearing so as to be sandwiched between the bearing portion 183 and the cam shaft holder 184 above the four lifter guide holes 182i arranged in a line in the front and rear direction.

An insertion hole 185 for fitting the spark plug 47 is provided between the guide holes 182e and 182e on the exhaust port 44 side.
In addition, a chain chamber 186 in which a cam sprocket 48s fitted on the rear portion of the cam shaft 48 and a timing chain 51 wound around the cam sprocket 48s are disposed is formed at the rear portion of the cylinder head 33.
A secondary air introduction passage 187 communicating with the exhaust port 44 is formed on the exhaust port 44 side.

  The intake valve 45 is reciprocally supported by the valve guide cylinder 181i and the lifter guide hole 182i of the cylinder head 33, and the exhaust valve 46 is reciprocally supported by the valve guide cylinder 181e and the guide hole 182e.

  That is, the intake valve 45 has its valve stem 45s fitted into the valve guide cylinder 181i, and a valve lifter 45l provided at the upper end of the valve stem 45s via the retainer 45r is slidably fitted into the lifter guide hole 182i. A valve spring 45sp is interposed between 45r and the fixed portion of the valve guide cylinder 181i.

  Further, the exhaust valve 46 has its valve stem 46s fitted into the valve guide cylinder 181e, and the screw 50a at one end of the rocker arm 50 is directly in contact with the upper end of the valve stem 46s, and the retainer 46r fitted into the upper end of the valve stem 46s. Is slidably fitted into the guide hole 182e, and a valve spring 46sp is interposed between the retainer 46r and the fixed portion of the valve guide cylinder 181e.

  Therefore, when the camshaft 48 rotates, the intake cam lobe 48i on the camshaft 48 directly presses the valve lifter 45l to reciprocate the intake valve 45 in parallel with the reciprocating direction of the piston 40 and open to the combustion chamber 42. The opening of 43 is opened and closed at a predetermined timing. At the same time, the exhaust cam lobe 48e on the cam shaft 48 swings the rocker arm 50, and the screw 50a at one end of the rocker arm 50 presses the upper end of the valve stem 46s to reciprocate the exhaust valve 46 The opening of the exhaust port 44 that moves and opens into the combustion chamber 42 is opened and closed at a predetermined timing.

  The outer wall 180 on the right side of the outer wall 180 that forms a generally rectangular frame of the cylinder head 33 has a recessed portion 33a in which a portion from which the intake port 43 extends is recessed inward, and the cylinder head cover overlapped with the cylinder head 33 A concave portion 34 a is also formed in the outer wall of 34 continuously to the concave portion 33 a of the cylinder head 33.

The intake port 43 extends to the cylinder head cover 34 side (substantially upward) along the recess 33a on the outer side surface of the right outer wall 180 of the cylinder head 33, and is far before reaching the same surface as the mating surface 180u with the cylinder head cover 34. , Connected to the intake manifold 20.
A connecting portion 43 a of the intake port 43 with the intake manifold 20 is located on the side of the lifter guide hole 182 i of the intake valve 45.

The intake manifold 20 connected to the intake port 43 extends substantially upward along a recessed portion 33a of the cylinder head 33 and a continuous recessed portion 34a of the cylinder head cover 34.
A fuel injection device 21I is interposed in the middle of the intake manifold 20 together with the throttle body 21.

  The intake port 43 extending substantially upward along the recess 33a formed on the right outer surface of the cylinder head 33 and having a small outward protrusion corresponds to the same surface as the mating surface of the cylinder head 33 and the cylinder head cover 34. Since it is connected to the intake manifold 20 at a side position of the lifter guide hole 182 of the intake valve 45 on the near side, the left and right width of the cylinder head 34 can be narrowed to reduce the size.

  As shown in FIG. 3, a pair of left and right upper pipes 3a, 3a of the center frame portion 3 extend in the front-rear direction on the left and right sides of the cylinder head cover 34, so that the throttle body 21 does not interfere with the right upper pipe 3a. 20 is connected to the throttle body 21 so as to extend upward between the cylinder head 33 and the right upper pipe 3a to substantially the same height as the mating surface of the cylinder head 33 and the cylinder head cover 34.

  The intake port 43 and the intake manifold 20 are curved and extend upward along a recess 33a formed on the right outer surface of the cylinder head 33. However, the fuel injection device 21I has a distance to the combustion chamber 42. By being short and attached to the right side of the throttle body 21 of the intake manifold 20, the fuel injection direction of the fuel injection device 21I can be directed to the opening opened in the combustion chamber 42 of the intake port 43 as shown in FIG. The fuel can be efficiently supplied to the combustion chamber.

  Further, as shown in FIG. 6, a connecting portion 43a between the intake port 43 and the intake manifold 20 is located on the side of the lifter guide hole 182i of the cylinder head 33 that slidably supports the valve lifter 45l of the intake valve 45. Therefore, the lifter guide hole 182i can be protected by the intake manifold 20.

  Further, the cam shaft 48 is pivotally supported so as to be sandwiched between the bearing portion 183 and the cam shaft holder 184 on the same surface as the mating surface 180u of the cylinder head 33 with the cylinder head cover 34. Further, since the intake manifold 20 extends substantially upward along the recesses 33a and 34a of the cylinder head 33 and the cylinder head cover 34, the intake manifold 20 can protect the camshaft 48.

It is a side view of the state which removed the body cover etc. of the rough terrain vehicle in which the power unit concerning one embodiment of the present invention was carried. It is the same top view. It is a rear view of the power unit. It is an expanded sectional view (IV-IV line sectional view of Drawing 3) of the power unit. It is sectional drawing (VV line of FIG. 3, V'-V 'line sectional drawing) of the power unit. It is principal part sectional drawing of an internal combustion engine. It is a top view of a cylinder head.

Explanation of symbols

P: power unit, E: internal combustion engine, T: transmission,
DESCRIPTION OF SYMBOLS 1 ... Vehicle for rough terrain travel, 2 ... Body frame, 20 ... Intake manifold, 21 ... Throttle body, 21I ... Fuel injection device, 22 ... Air cleaner, 23 ... Exhaust pipe, 24 ... Exhaust muffler,
29 ... Intake connecting pipe, 30 ... Crankshaft, 31L ... Lower crankcase, 31U ... Upper crankcase, 32 ... Cylinder block, 33 ... Cylinder head, 33a ... Recess, 34 ... Cylinder head cover, 34a ... Recess,
40 ... piston, 42 ... combustion chamber, 43 ... intake port, 44 ... exhaust port, 45 ... intake valve, 46 ... exhaust valve, 47 ... ignition plug, 48 ... cam shaft, 49 ... rocker arm shaft, 50 ... rocker arm,
180 ... outer wall, 180u ... mating surface, 181i, 181e ... valve guide tube, 182i ... lifter guide hole, 182e ... guide hole, 183 ... bearing portion, 184 ... cam shaft holder.

Claims (3)

An intake valve is supported by a cylinder head integrally formed with an intake port so as to reciprocate in parallel with the reciprocating direction of the piston, and a fuel injection device integrated with a throttle body is provided in an intake manifold connected to the intake port. In internal combustion engines
The intake port extending toward the cylinder head cover along a recess formed on the outer surface of the cylinder head is connected to the intake manifold before reaching the same plane as the mating surface of the cylinder head and the cylinder head cover. An intake structure for an internal combustion engine, which is characterized.   2. The internal combustion engine according to claim 1, wherein a connection portion between the intake port and the intake manifold is located on a side of a lifter guide hole of the cylinder head that slidably supports a valve lifter of the intake valve. Intake structure. The camshaft that directly presses the intake valve is located on the mating surface of the cylinder head and the cylinder head cover,
A concave portion that is continuous with the concave portion of the cylinder head is also formed in the cylinder head cover that is overlapped with the cylinder head,
The intake structure for an internal combustion engine according to claim 1 or 2, wherein the intake manifold connected to the intake port extends along the recess of the cylinder head cover.

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